Present work concentrates on the metabolism of specific brain proteins and on the effect of protein free diet on protein turnover. The developmental pattern of specific amino acid transsport systems will also be studied. We have developed a method for measuring long term (5 days) incorporation in brain and we are now studying incorporation into the protein components of myelin and into tubulin. The rate of breakdown of these proteins by purified brain proteases is compared to their rate of turnover in vivo. We are trying to extend such studies to other purified brain proteins such as S100 and neurostenin. Studies of protein malnutrition will focus on the control of amino acid pool and the limiting amino acid that affects cerebral protein synthesis. The study of development of amino acid transport will focus on perinatal appearance of the various amino acid transport classes. First each class will be delineated with specific inhibitors and measuring affinities, then uptake will be measured in brain perfusion, in isolated capillaries and in brain slices. BIBLIOGRAPHIC REFERENCES: Lajtha, A. and Sershen, H., "Changes in Amino Acid Influx with Na ion Flow in Incubated Slices of Mouse Brain," Brain Research 84, 429-441 (1975). Lajtha, A. and Sershen, H., "Inhibition of Amino Acid Uptake by the Absence of Na ion in Slices of Brain," 24, 667-672 (1975).